The present invention relates to a sputtering target comprising an Al—Te—Cu—Zr alloy and a method of manufacturing thereof. In particular, the present invention relates to an Al—Te—Cu—Zr alloy sputtering target for forming a thin film comprising an Al—Te—Cu—Zr alloy as a variable resistance material, and a method of manufacturing thereof.
As variable resistance recording materials, thin films comprising Te—Al based materials and Te—Zr based materials have been used in recent years for recording information by taking advantage of resistance change. Thin films comprising such materials are commonly formed by a so-called physical vapor deposition method such as the vacuum deposition method and the sputtering method. In particular, the magnetron sputtering method is often used in view of operativity and stable film formation.
A method of forming a thin film by the sputtering method involves physically bombarding positive ions such as argon ions to a target placed at an cathode to eject a material of the target by means of the collision energy, thereby depositing a film having the substantially same composition as the material of the target on a facing substrate at the cathode side. Deposition by the sputtering method is characterized by that films having thicknesses ranging from as thin as angstroms to as thick as tens of micrometers can be formed at a stable deposition rate by adjusting processing time, input power and the like.
A particular problem in forming an alloy film such as a Te—Al based alloy as a variable resistance recording material is nodule formation on the surface of a target during sputtering, which may be responsible for particles and arcing. Since an Al—Te—Cu—Zr alloy target is configured from various metal components having different deposition rates, there is a problem in more frequent formation of nodules and a large amount of particle generation. The target and sputtering problem as described above accounts in no small part for decrease in the quality of a thin film as a recording medium.
As a conventional Te—Al based sputtering target, Patent Document 1, for example, discloses a target comprising one or more high-melting-point metal elements selected from the element group of Ti, Zr, Hf, V, Nb, Ta, and lanthanoid elements; one or more elements selected from Al, Ge, Zn, Co, Cu, Ni, Fe, Si, Mg and Ga; and one or more chalcogen elements selected from S, Se and Te. A method of manufacturing the above target is also disclosed, the method comprising: producing an AlCuZr alloy ingot; then pulverizing the alloy ingot to prepare an alloy powder; mixing the alloy powder with a Te powder and a Ge powder; and sintering the resulting mixture to manufacture an AlCuGeTeZr target material (see Example 1).
Unfortunately, alloying of Al and Te for production of a sintered compact comprising a Te—Al based alloy may generate Al—Te which is highly reactive and requires complicated handling. In addition, the large vapor pressure of Te may result in a composition deviation when synthesized with a high-melting-point material such as Zr (the vapor pressure at 1000° C. is 100 kPa for Te and 1 kPa or less for Zr). Further, significantly different sputtering rates of constituent phases may disadvantageously result in heterogeneous deposition rates and nodule formation on the surface of a sputtering target, which may, in turn, be responsible for particle generation.